Modular femoral fixation system

ABSTRACT

A modular femoral internal implant system for use in the treatment of femoral disorders resulting from injury, disease or congenital defect includes at least three interconnectable components: (1) an elongated epiphyseal/metaphyseal implant, (2) an intramedullary rod and (3) an angled side plate having an elongated plate portion adapted to be secured to the outer cortical wall and a hollow sleeve adapted to extend into the femur. The epiphyseal/metaphyseal implant can be connected to either the angled side plate or the intramedullary rod. The system may also include an elongated bone plate connectable to the angled side plate, one or more additional epiphyseal/metaphyseal implants of variable length, an additional angled side plate, a distal buttress plate connectable to the elongated bone plate, and a plurality of bone screws of a universal design. Preferably, many or all of the components of the system are made of an inert, resilient titanium-base alloy.

BACKGROUND OF THE INVENTION

Internal fixation of femoral fractures is one of the most commonorthopedic surgical procedures. Many different types of femoralfractures are encountered in practice, including fractures in thefemoral neck, intertrochanteric, mid-shaft and distal condylar regions.The femoral bone will sometimes fracture cleanly into two largefragments along a well-defined fracture line, and on other occasionsfracture into many smaller fragments. Often, more than one type offracture will exist concurrently in different regions of the femur of aninjured patient.

A wide variety of implants have been developed over the years for use inthe internal fixation of femoral fractures. Although numerous excellentdesign achievements have been realized, several general problem areasremain. First, almost all of the currently available implants have ahighly specialized application limited to only one specific anatomicallocation in the femur. Thus, a hospital must maintain at great expense avery large and variegated inventory of different implants to handle allexpected contingencies. These implants are generally not compatible,i.e. they cannot be interconnected together in case of a complicatedfracture pattern extending into different anatomical regions of thefemur. Second, each implant has its own peculiar attributes anddeficiencies, and the use of many of the known implants involves the useof a surgical technique that is unique to that implant and sometimescomplicated and difficult as well. Consequently, the opportunities forimproper implant selection and surgeon error during implantation areinevitably increased. Finally, tissue reactions with implants made ofstainless steel and certain other surgical implant alloys tend to reducethe useful lifetime of the implants and require premature removal fromthe patient's body.

One very commonly utilized femoral internal fixation device is anelongated implant (nail, screw, pin, etc.) adapted to be positionedalong the longitudinal axis of the femoral neck with its leading endportion in the femoral head so as to stabilize a fracture of the femoralneck. The elongated implant may be implanted by itself or connected toanother implant such as a side plate or intramedullary rod. The leadingend portion of the implant typically includes means to positively gripthe femoral head bone (external threads, expanding arms, etc.), but theinclusion of such gripping means can introduce several significantproblems. First, implants with sharp edges on the leading end portion,such as the externally threaded implants, exhibit a tendency to migrateproximally towards the hip joint bearing surface after implantation.Such proximal migration under physilogical loading, which is alsoreferred to as femoral head cut-out, can lead to significant damage tothe adjacent hip joint. Also, the externally threaded implants cangenerate large stress concentrations in the vicinal bone duringimplantation which can lead to stripping of the threads formed in thebone and thus obviously a weakened grip. The movable arms of knownexpanding arm devices are usually free at one end and attached at theother end to the main body of the leading end portion of the implant. Asa result, all fatigue loading is concentrated at the attached ends ofthe arms and undesirably large bending moments are realized at thepoints of attachment.

As stated above, known elongated implants used to stabilize fractures ofthe femoral neck are often connected in use to a side plate which inturn is secured to the outer cortical wall of the adjacent femoralshaft, for example with bone screws. This type of assembly is oftenselected when a femoral neck fracture is a part of a more complicatedfracture pattern including also one or more fractures in the metaphysealand/or diaphyseal regions of the femur. Clearly, the surgeon desires tobe able to select the appropriate length of the side plate dependingupon the particular traumatic condition of the patient's femur. However,the surgeon's flexibility in this regard typically requires the hospitalto maintain a costly inventory of implants.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a modular system offemoral internal implants, and instrumentation therefor, that can beemployed to treat a number of different fracture patterns and otherdisorders with a minimal number of interconnectable system componentsinvolving simple uncomplicated operational procedures in which surgicalinvasiveness and operation times are minimized.

This and other objects of the invention are achieved with a novel kitfor use in the amelioration of a number of different types of femoraldisorders resulting from injury, disease or congenital defect with aminimal number of interconnectable components. The kit comprises atleast the following components: (1) an elongated epiphyseal/metaphysealimplant having a leading end portion and a trailing end portion andadapted to grip bone at its leading end portion; (2) an intramedullaryrod having a distal end and a proximal end; (3) an angled side platecomprising an elongated plate portion adapted to be secured to the outercortical wall of the femoral shaft and an integral hollow sleeveextending at an angle from one end of the plate portion so that saidhollow sleeve extends into the femur when the plate portion is securedto said cortical wall; and (4) means for connecting theepiphyseal/metaphyseal implant to the intramedullary rod adjacent to oneof the ends of the rod with the epiphyseal/metaphyseal implant at anangle with respect to the intramedullary rod.

According to the invention, the components of the novel kit aredimensioned such that the elongated epiphyseal/metaphyseal implant iscapable of being connected to the angled side plate by the insertion ofthe trailing end portion of the epiphyseal/metaphyseal implant into thehollow sleeve of the angled side plate and the elongatedepiphyseal/metaphyseal implant is also capable of being connected to theintramedullary rod with the use of said connecting means. Thus the sameepiphyseal/metaphyseal implant can be either connected to theintramedullary rod, to form for example a Y-nail type of assembly totreat an unstable subtrochanteric fracture pattern, or connected to theangled side plate, to form for example a side plate-pin assembly totreat a different fracture pattern. The intramedullary rod may be eitherconnected to the elongated epiphyseal/metaphyseal implant or implantedindependently of said implant and the angled side plate.

The novel kit can be used to treat a variety of trauma conditions aswell as to ameliorate other types of femoral disorders includingnon-unions, congenital deformities and pathological deformities (e.g.Paget's disease), and can also be utilized in the prophylactic fixationof weakened bone, bone defects, etc., and in the performance ofosteotomies. Simple and uncomplicated surgical techniques can beemployed and operating times and implant inventories kept at a lowlevel.

As used herein the term "elongated epiphyseal/metaphyseal implant"refers to an elongated implant adapted to be used in such a manner thatit extends after implantation from the epiphyseal region of the proximalfemur into the adjacent metaphyseal region, or from the lateral to themedial epiphyseal region of the distal femur. In general, the elongatedepiphyseal/metaphyseal implant can be a pin, nail, screw, etc.Preferably, the intramedullary rod is axially cannulated and is providedwith at least one through bore adjacent its distal end for reception ofa locking screw.

The modular femoral implant system advantageously includes componentsadditional to the essential epiphyseal/metaphyseal implant,intramedullary rod, angled side plate and epiphyseal/metaphysealimplantintramedullary rod connection means. Thus, the kit preferablyincludes an elongated bone plate adapted to be secured to the outercortical wall of the femoral shaft. The elongated bone plate and angledside plate are dimensioned such that the elongated bone plate can beconnected to the plate portion of the angled side plate to provide anextension of the effective length of said plate portion without havingto inventory two complete angled side plates. The elongated bone platecan of course be utilized by itself in a conventional manner, ifdesired. Most preferably, several elongated bone plates of variablelength are included in the kit.

In a further preferred embodiment of the invention the kit includes adistal buttress plate including a relatively flat elongated proximalportion adapted to be secured to the lateral distal femoral shaft and arelatively curved distal portion adapted to be secured to the lateraldistal femoral condyle. In this embodiment the kit includes at least oneelongated bone plate that is capable of being connected to each of theplate portion of the angled side plate and the proximal portion of thedistal buttress plate for effective length extension purposes, asdesired.

The novel kit of the present invention preferably includes a pluralityof threaded self-tapping cortical bone screws for use in securing theelongated plate portion of the one or more angled side plates to theouter cortical wall of the femoral shaft and, when the kit includes anintramedullary rod with a distal through bore and one or more elongatedbone plates, securing the distal end of the intramedullary rod to thedistal femur, securing said bone plate(s) to the outer cortical wall ofthe femoral shaft, and connecting said plate portion(s) and boneplate(s) together in axial alignment. The kit preferably includes aplurality of such screws each having a head and a threaded shank, withsaid screws being identical except for variations in the length of thethreaded shanks. Although not every one of these screws can be used inall of the capacities set forth above (for example short cortical screwscnnot be used to secure the distal end of the intramedullary rod), theprovision of a plurality of threaded self-tapping cortical bone screwsof universal screw head and screw shank design (except for variations inscrew shank length) provides substantial opportunities forinterchangeability in use and reduced inventory levels, and requires thesurgeon to be familiar with only one set of cortical screwcharacteristics, attributes and techniques of use. Furthermore, saidbone screws can be used independently as bone fixation screws to holdfragments of bone together during healing of a fracture. Mostpreferably, the heads of the cortical screws and the apertures in theplate portion(s) and bone plate(s) intended to receive them areconfigured in such a manner that the screws are capable of a universalrotation with respect to the plate portion or bone plate within a conehaving an apex angle of at least about 20° when the screw head is fullyadvanced into the aperture receiving it. Thus, for example, theunderside of the universal screw head may be spherically rounded (convextowards the bone) and the abutting surfaces of the screw-receivingapertures complimentary thereto (and of course concave away from thebone).

Preferably, the components of the novel kit of the invention are made ofa resilient, physiologically inert titanium-base alloy such asTi-11.5Mo-6Zr-4.5Sn, Ti-6Al-4V or Ti-3Al-2.5V. The physiologicalinertness of such alloys reduces the potential for adverse tissuereactions (as compared to e.g. stainless steel) and thus will serve toincrease product lifetime in vivo after implantation. Also, most of thecurrently available implants for the internal fixation or ameliorationof femoral fractures or other disorders are made of highly rigidmaterials, thus leading in many circumstances to excessive "stressshielding" in which too much of the stresses applied to the femur areborne by the implant rather than the healing bone in the fractureregion. Stress shielding may delay fracture healing and weaken thesurrounding bone. This problem of stress shielding is greatly alleviatedby making the components of the kit out of a resilient titanium-basealloy.

In a preferred distribution of components, the kit comprises: (1) twoepiphyseal/metaphyseal implants of different length, (2) an angled sideplate in which the hollow sleeve and plate portion are mutually orientedat an oblique angle so that the hollow sleeve is adapted to extend intothe intertrochanteric region when the plate portion is secured to theouter cortical wall of the adjacent femoral shaft, (3) an angled sideplate in which the hollow sleeve and plate portion are substantiallyperpendicular so that the hollow sleeve is adapted to extend into thedistal condylar region of the femur when the plate portion is secured tothe outer cortical wall of the adjacent distal femoral shaft, (4) anintramedullary rod (preferably having a through bore adjacent its distalend), (5) means for connecting the shorter of the twoepiphyseal/metaphyseal implants to the intramedullary rod adjacent tothe proximal end of the rod to form a Y-nail type of assembly, (6) aplurality of cancellous and cortical bone screws, and (7) at least oneelongated bone plate capable of being connected in axial alignment tothe plate portion of each of the angled side plates for effective lengthextension purposes. The shorter epiphyseal/metaphyseal implant is alsocapable of being connected to the substantially perpendicularly-angledside plate, while the longer epiphyseal/metaphyseal implant is capableof being connected to the obliquely-angled side plate. With this highlypreferred distribution of components, the components of the kit can beassembled together in different ways or used independently to treat orameliorate most of the femoral fracture conditions and other femoraldisorders commonly encountered by orthopedic surgeons.

In addition to the overall modular concept of the femoral implantsystem, the present invention is also directed to the particular designof various of the components of the system. Thus, included within theconcept of the present invention is a novel bone implant for use in thestabilization of a bone fracture comprising an integral substantiallycylindrical expansion sleeve having a smoothly roundedcircumferentially-closed dome at one end, a circumferentially-closedcircular ring at its other end, and a plurality of thin elongated stripsextending between, and connected at their opposed ends to, thecircumferentially-closed dome and ring, said strips being of varyingradial thickness along their length and having textured outer surfaces;and an elongated plunger having at one end thereof a substantiallycylindrical body portion having a diameter essentially equal to theinner diameter of the circumferentially-closed circular ring of theexpansion sleeve. When the expansion sleeve is held in a cavity in abone fragment on one side of a fracture and the plunger is advancedthrough said circular ring and into the interior of the sleeve with itssubstantially cylindrical body portion in the leading position, theplurality of thin elongated strips in the sleeve are caused to expandradially outwardly and thereby securely grip the bone fragment. Thenovel bone implant of this aspect of the invention can be, but is notnecessarily, an epiphyseal/metaphyseal implant.

As used herein the topographical term "circumferentially-closed" meansthat a path can be traced entirely around the circumference of a hollowstructure having an axis while avoiding any break or gap or otherinterruption in the solid material of the structure. Thus, for example,a split ring would not be circumferentially-closed, while a closed ringwould be. The uninterrupted path may be irregular in contour but must becontinuous for a full 360° with respect to the axis of the structure inquestion.

Because the expansion sleeve of the bone implant of this aspect of theinvention has a smoothly rounded circumferentially-closed dome at itsleading end, the likelihood of significant proximal implant migration or"cut-out" in the femoral head is greatly reduced (as compared, forexample, to an externally-threaded bone screw or tri-flanged nail). Thisis a very important feature giving rise to substantially improvedproduct life and substantially reduced bone damage. The feature that theexpandable strips in the expansion sleeve extend between, and areconnected at their opposed ends to, two circumferentially-closedstructures (i.e. the smoothly rounded dome at the leading end of theexpansion sleeve and the circular ring at the trailing end) is alsosignificant since it means that these thin strips have no free ends thatcan contribute to cut-out or catch on the wall of a prepared cavity inthe patient's bone structure during implantation. No significant torque(which can cause rotation of the femoral head during insertion orstripping of the bone material) has to be applied to the implant duringits implantation, and the radial expansion of the textured stripsprovides a highly effective and secure bone gripping action distributedalong the surface of the sleeve without generating excessive stressconcentrations in the bone adjacent the implant. Additionally, becausethe expandable strips are anchored at both ends fatigue loading is notconcentrated at one end of the strip and bening moments are more evenlydistributed along the strip.

The actuation mechanism of this novel expansion sleeve implant is simpleand foolproof and includes no complicated moving parts that mightmalfunction during implantation. Preferably, the plunger includes araised annular rib adjacent the trailing end of the plunger bodyportion, which rib is adapted to fit into a corresponding grooveprovided in the inner wall of the circular ring of the expansion sleevewhen the plunger is fully advanced within the sleeve. This rib andgroove combination serves to lock the plunger and sleeve againstundesired relative axial displacement after implantation.

It is highly preferred that the expansion sleeve be made of a resilientmaterial such as a titanium-base alloy. In this case, the resilientstrips of the expansion sleeve will expand radially outwardly in elasticdeformation when the plunger is advanced into the sleeve and will revertto their original shape (to facilitate removal of the sleeve, ifdesired) when the plunger is withdrawn. Also, whether or not the sleeveis made of a resilient material, it is desirable to design it so thatopenings are provided in the sleeve in its rest position. An extrudablematerial such as a bone cement for enhancement of the bone implantfixation can be placed into the sleeve and then extruded through theseopenings to the bone-implant interface as the plunger is advanced. Thedesired openings in the sleeve can be distinct gaps between the stripsin the rest position of the sleeve, or some other type of opening.

In a preferred surgical implantation technique, a guide wire is placedinto the patient's bone at the desired location, a substantiallycylindical cavity to receive the implant is formed with a drill orreamer cannulated to fit over the guide wire, the expansion sleeve issecured (preferably releasably) at its smoothly rounded dome to anelongated cannulated rod (carrying the plunger) which extends within theexpansion sleeve and through the circumferentially-closed circular ringthereof, the expansion sleeve is inserted into and held in place withinthe prepared cavity in the bone by means of the elongated rod (whichfits over the guide wire), and the plunger is advanced along saidinsertion rod into the interior of the expansion sleeve. Morepreferably, the insertion rod is externally threaded at one end and thedome of the expansion sleeve is provided with a centrally-disposedthreaded axial through bore for the releasable attachment of theexternally threaded end of the insertion rod.

The present invention also includes a preferred instrument for use ininserting a surgical implant (e.g. the novel expansion sleeve-containingbone implant of the invention discussed above) into a cavity in apatient's bone. This novel insertion instrument comprises an elongatedaxially cannulated rod having an externally threaded portion adjacentone of its ends and an externally smooth portion extending from theexternally threaded portion towards the other end of the rod; a hollowsleeve receiving the elongated rod, which sleeve is capable of slidingmovement upon the externally smooth portion of the rod; and means foradvancing the hollow sleeve along the externally smooth portion of theenlongated rod towards the externally threaded portion of the rod. Thesleeve advancing means is preferably structured in such a way that itpositively prevents movement of the hollow sleeve along the rod in adirection away from the externally threaded portion of the rod while itis engaged with the sleeve. Suitable sleeve advancing means include aknurled knob threaded upon a second externally threaded portion of theelongated rod on the opposite side of the externally smooth portion thanthe aforementioned first externally threaded portion, or a spreader toolwhich interacts with ratchets provided on the elongated rod on saidopposite side of its externally smooth portion.

By using the preferred implantation technique and insertion instrumentdescribed above, with the hollow sleeve of the instrument positionedbehind and forcing the plunger of the implant into the expansion sleeve,the novel expansion sleeve and plunger-containing bone implant of theinvention can be readily inserted into the prepared cavity in thepatient's bone in a simple surgical procedure involving low consumptionof time and minimal risk of surgical error or equipment malfunction andhaving highly reproducible results from case to case. The same insertioninstrument can be used with bone implants of different length. Thefeature that the sleeve advancing means positively prevents rearwardmovement of the sleeve along the rod is significant because it permitsthe surgeon to readily stop advancement of the plunger during itsinsertion into the expansion sleeve without releasing the compressiveforce being placed upon the plunger by the hollow sleeve of theinsertion instrument.

Another aspect of the present invention is a novel elongated bone platehaving an upper surface intended to face away from the patient's bonethat is wider than a lower surface intended to face towards thepatient's bone, and two side surfaces connecting the upper and lowersurfaces which are tapered inwardly toward one another in the directionfrom the upper surface to the lower surface. The bone plate has asubstantially constant thickness between the two side surfaces and isadapted to be secured to a patient's bone by means of bone fastenersreceived in apertures in the bone plate. Because the lower surfaceadjacent the bone is thinner (preferably 70% to 90% in width) than theupper surface at which stresses from physiological bending momentsapplied to the plate tend to be at a maximum, the necessary periostealtissue stripping adjacent the bone for implantation purposes can bereduced without excessively sacrificing the strength of the bone plateunder bending. In one preferred embodiment said upper and lower surfacesare defined in transverse bone plate cross-section by arcs of twoconcentric circles, while the two side surfaces are defined therein bytwo straight radial lines passing through the common center of saidconcentric circles.

It is also preferred that an elongated bone plate of this aspect of theinvention comprise two parallel integral downwardly-extending railslocated at opposite sides of the lower surface and extending alongsubstantially the entire length of the bone plate. These two rails serveto lift the lower surface of the bone plate away from the surface of thepatient's bone so as to permit enhanced vascularization of the bonedirectly beneath the lower surface and thus avoid any excessiveweakening of that bone tissue.

As has been discussed above in connection with the modular femoralimplant kit or system of the invention, it is highly advantageous toprovide an elongated bone plate that can be readily connected to theelongated plate portion of another surgical implant in a simple,foolproof, non-time consuming surgical method so as to effectivelyprovide an extension of the length of said elongated plate portion. Theother surgical implant may be, for example, another bone plate, anangled side plate, a distal buttress plate, or the like. Thus, a furtheradvantage of the novel elongated bone plate of the invention is that itcan be readily connected to a surgical implant having an elongated plateportion adapted to be secured to a patient's bone by means of bonefasteners received in apertures in the elongated plate portion, whichplate portion has upper and lower surfaces, with a cavity being formedin the lower surface of the plate portion at a free end thereof, saidcavity extending longitudinally from said free end to a shoulderdefining an end of the cavity and said cavity having a transversecross-section complementary to that of the elongated bone plate of theinvention. An important consequence of the complementary designs of thetransverse cross-sections, including downwardly-inwardly tapered sidewalls, of the surgical implant cavity and elongated bone plate is thatthe bone plate "dovetails" with the surgical implant so that it canenter and be removed from the cavity in the surgical implant only byrelative axial movement through the cavity opening at the free end ofthe elongated plate portion of the surgical implant. Also, no relativerotation is permitted between the surgical implant and bone plate. Whenthe end of the bone plate abuts the shoulder at the other end of thecavity, no relative translational movement is possible between thesurgical implant and bone plate except for axial separation. By insuringthat at least one bone fastener-receiving aperture in the elongatedplate portion of the surgical implant overlies a bone fastener-receivingaperture in the bone plate when the plate is inserted into said cavityin the surgical implant and abuts the shoulder at the end of the cavity,a stable and secure assembly of surgical implant and bone plate, inwhich the length of the elongated plate portion of the surgical implantis effectively extended by the elongated bone plate, can be realizedwhen the assembled surgical implant and bone plate are secured togetherto the patient's bone.

The present invention comprises additionally a novel distal buttressplate adapted to be secured to the outer cortical wall of the lateraldistal femur by means of bone fasteners received in aperture in theplate. The plate includes a relatively flat elongated proximal portionadapted to be secured to the lateral distal femoral shaft and arelatively curved distal portion, curved out of the plane of theproximal portion, adapted to be secured to the lateral distal femoralcondyle.

For injuries including a sagital fracture through the distal epiphysealbone, it is highly desirable to use a distal buttress plate inconjunction with at least two lag screws used for fracture reduction inthe distal condylar region, with these lag screws being positionted inclose proximity to, but not passing through, the distal portion of thebuttress plate. Thus, in accordance with this aspect of the invention,two spaces for the accommodation of a pair of lag screws are leftadjacent the sides of a thin neck connecting a wider, generally roundedhead at the distal end of said distal portion and a still wider distalportion body having a greater maximum width than the elongated proximalportion of the buttress plate. Preferably, at least one elongatedaperture capable of receiving two bone fasteners is provided in thedistal portion head and a pair of such elongated apertures, one on eachside of the body, are provided in the distal portion body. It is alsopreferred that the relatively flat proximal portion of the buttressplate be provided with an appropriately dimensioned cavity for a"dovetailed" connection to the novel bone plate of the invention in themanner and for the purposes described above.

Yet another aspect of the present invention is directed to a novel boneimplant assembly for the stabilization of a fractured femur comprisingan elongated cross-member having a leading portion adapted to bereceived within a cavity in the femoral head and grip the femoral headand a trailing portion adapted to extend from the leading portion intothe intertrochanteric region of a patient's femur, with said trailingportion being provided with a cylindrical through bore, which throughbore is at an oblique angle with respect to the longitudinal axis of thecross-member so that it can be brought into approximate alignment withthe femoral intramedullary canal when the leading portion of thecross-member is inserted into the femoral head; and intramedullary rodhaving a distal end portion and a proximal end portion, with the maximumdiameter of said proximal end portion being just slightly less than thatof the cylindrical through bore in the trailing portion of the elongatedcross-member so that said proximal end portion can be received in aclose sliding fit within said through bore permitting rotational andtranslational adjustment of the cross-member with respect to theintramedullary rod; and distinct, positive and active means toreleasably lock the elongated cross-member and intramedullary rod toprevent their relative translational and rotational movement whenassembled together. The elongated cross-member may be a single integralpiece or, alternatively, may comprise two or more non-integral piecesadapted to be connected in use. Thus, for example, the cross-member maycomprise a first piece adapted to grip the femoral head and a secondpiece non-integral therewith adapted to be releasably locked to theintramedullary rod and adapted to receive the first piece in use in anunlocked sliding fit. As used herein, the term "distinct, positive andactive means to releasably lock the elongated cross-member andintramedullary rod" refers to one or more structural elements, distinctfrom the surfaces of the elongated intramedullary rod and the throughbore in the cross-member, that are capable of actuation after theintramedullary rod and the cross-member have already been assembledtogether to effect a positive releasable locking of the intramedullaryrod and cross-member. The presence of such releasable locking means,e.g. a locking screw in an internally threaded bore in the cross-memberadapted to be screwed so as to firmly press a locking shoe against theproximal end portion of the intramedullary rod, greatly facilitates theobtaining of the precise desired relative disposition of theintramedullary rod and elongated cross-member in a particular clinicalcase.

Preferably, the elongated intramedullary rod has acircumferentially-closed cross-section and is provided with a pluralityof longitudinal splines around its circumference to prevent axialrotation of the implanted rod with respect to the patient's femur andprovide enhanced vascularization of bone tissue adjacent the rod outersurface, and the releasable locking means comprise a locking screw andlocking shoe held within a bore in the cross-member. The locking shoehas an exterior surface that is complementary to thelongitudinally-splined outer surface of the intramedullary rod, andwhich is pressed against the outer surface of the intramedullary rodwhen the locking screw is advanced in said bore. More preferably, theelongated cross-member and the intramedullary rod are made of aresilient titanium-base alloy. Most preferably, the intramedullary rodis an extruded hollow body made of Ti-3Al-2.5V alloy.

Additionally, another aspect of the present invention is a novelcancellous or cortical bone screw made of a resilient titanium-basealloy having a head and a partially or fully threaded shank, with anaxially-extending recess of generally star-shaped cross-section (e.g. aTorx(™)-drive or Pozidriv (™) recess) having substantially parallelaxially-extending walls being provided in the screw head for receipt ofa driving instrument for the screw. The design of the drivinginstrument-receiving recess of the novel screw renders the screw farless susceptible to fretting than e.g. a slotted screw, therebyfacilitating its insertion into a patient's bone and making practicalthe use of a resilient titanium-base alloy as the material ofconstruction for the screw.

Other aspects of the present invention will be apparent from a readingof the specification and claims herein in their entirety.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in detail with reference to variouspreferred embodiments thereof. Reference to these embodiments does notlimit the scope of the invention, which is limited only by the scope ofthe claims. In the drawings:

FIG. 1 is an exploded side elevational view of an epiphyseal/metaphysealimplant of the present invention including an expansion sleeve and anelongated plunger;

FIG. 2 is a longitudinal sectional view of the expansion sleeve of theimplant of FIG. 1 in the rest position of the sleeve, taken along aplane including the longitudinal axis of the sleeve;

FIG. 2A is an end view of the expansion sleeve of FIG. 1 in the restposition of the sleeve;

FIGS. 3 to 5 are longitudinal sectional views of the implant of FIG. 1,taken along a plane including the common longitudinal axis of theplunger and sleeve, showing three stages in the insertion of the plungerinto the sleeve held in a patient's bone;

FIG. 6 is a top plan view of a proximal angled side plate included in amodular implant system or kit of the invention;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 6;

FIG. 8 is a sectional view taken along line 8--8 of FIG. 6;

FIG. 9 is a top plan view of an elongated bone plate included in amodular implant system of the invention;

FIG. 10 is a sectional view taken along line 10--10 of FIG. 9;

FIGS. 11A and 11B are side elevational views of a pair of cortical bonescrews of different shank lengths included in a modular implant systemof the invention;

FIGS. 12A and 12B are side elevational views of a pair of cancellousbone screws of different shank lengths included in a modular implantsystem of the invention;

FIG. 13 is an enlarged top plan view of each of the cortical bone screwsof FIGS. 11A and 11B;

FIG. 14 is a sectional view taken along line 14--14 of FIG. 9 showingthe permitted side-to-side angulation of one of the cortical bone screwsof FIG. 11A within one of the bone screw-receiving apertures provided inthe bone plate of FIG. 9;

FIG. 15 is a lateral elevational view of the epiphyseal/metaphysealimplant of FIG. 1, the proximal angled side plate of FIG. 6, theelongated bone plate of FIG. 9 and a plurality of cortical bone screwsof the type shown in FIGS. 11A and 11B, all connected together andsecured to a patient's femur, with the femur shown partly in section;

FIG. 16 is a sectional view taken along line 16--16 of FIG. 15;

FIG. 17 is a sectional view taken along line 17--17 of FIG. 15;

FIG. 18 is a side elevational view of a surgical implant insertioninstrument of the invention shown assembled with the expansion sleeveand elongated plunger of the implant of FIG. 1;

FIG. 18A is a sectional view taken along line 18A--18A of FIG. 18;

FIG. 19 is a side elevational view of an intramedullary rod having ananterior-posterior bow included in a modular implant system of theinvention;

FIG. 20 is another side elevational view of the intramedullary rod ofFIG. 19, as viewed in a direction perpendicular to that of FIG. 19;

FIG. 21 is a sectional view taken along line 21--21 of FIG. 19;

FIG. 22 is a longitudinal view, partially in section, of a proximal endregion of an intramedullary rod of the type shown in FIG. 19,illustrating the optional feature of a detachable hollow sleeve securedto the proximal end portion of the intramedullary rod;

FIG. 23 is a top plan exploded view of an elongated intramedullaryrod-epiphyseal/metaphyseal implant connection piece, locking screw andlocking shoe included in a modular implant system of the invention;

FIG. 24 is a front view, partially in section, of the articles shown inFIG. 23;

FIG. 25 is an elevational view of an epiphyseal/metaphyseal implant ofthe type shown in FIG. 1 but of shorter length, the intramedullary rodof FIG. 19 and the connection piece, locking screw and locking shoe ofFIG. 23, all connected together and secured to a patient's femur, withthe femur shown in section, wherein the epiphyseal/metaphyseal implantand connection piece form together an elongated cross-member;

FIG. 26 is a bottom plan view of a distal angled side plate included ina modular implant system of the invention;

FIG. 27 is a sectional view taken along line 27--27 of FIG. 26;

FIG. 28 is an elevational view of an epiphyseal/metaphyseal implant ofthe type shown in FIG. 1 but of shorter length, the distal angled sideplate of FIG. 26, the elongated bone plate of FIG. 9 and a plurality ofcortical bone screws of the type shown in FIGS. 11A and 11B, allconnected together and secured to a patient's femur, with the femurshown in section;

FIG. 29 is a top plan view of a distal buttress plate included in amodular implant system of the invention;

FIG. 30 is a side elevational view of the distal buttress plate of FIG.29;

FIG. 31 is an elevational view of the distal buttress plate of FIG. 29,the elongated bone plate of FIG. 9 and a plurality of cortical andcancellous bone screws of the type shown in FIGS. 11A, 11B, 12A and 12B,all connected together and secured to a patient's distal femur, with thefemur shown in section; and

FIGS. 32A and 32B are side elevational view of a pair of cortical bonescrews of different shaft lengths suitable for use as distal lockingscrews.

Except as otherwise indicated, all of the implants shown in FIGS. 1 to32B depicting various preferred embodiments of the invention are made ofa resilient, physiologically-inert titanium-base alloy.

An elongated epiphyseal/metaphyseal implant 1 of the invention is shownin FIG. 1. Implant 1 comprises an integral substantially cylindricalexpansion sleeve 3 and an elongated plunger 5. Sleeve 3 includes asmoothly rounded circumferentially-closed dome 7 at one end, acircumferentially-closed circular ring 9 at the opposite end, and aplurality (eight in the embodiment shown in FIGS. 1 to 5) of identicalsubstantially straight elongated thin resilient strips 11 extendingbetween, and connected at their opposed end by and to, dome 7 and ring9. A centrally-disposed threaded axial through bore 15 is provided indome 7 for releasably securing an elongated insertion rod to the dome.Strips 11 have textured outer surfaces to enhance the bone-grippingaction of the implant and define together the cylindrical wall of sleeve3, which sleeve wall has in the rest position of the sleeve an outerdiameter essentially equal to the outer diameter of ring 9. As is shownin FIG. 2, each of the strips 11 is of varying thickness along itslength so that the sleeve wall has in the rest position of the sleeve inan inner diameter in a region r₁ adjacent ring 9 equal to the innerdiameter of ring 9 and an inner diameter in a region r₂ spaced from ring9 reduced from the inner diameter of ring 9. The strips 11 do not toucheach other along their lengths in the rest position of the sleeve, butare instead separated by an equal number of longitudinal openings, e.g.13.

Plunger 5 includes at one end thereof a substantially cylindrical bodyportion 17 having a diameter essentially equal to the inner diameter ofring 9 of sleeve 3, and a cylindrical stem portion 19 having a smallerdiameter than body portion 17 extending from body portion 17 to theother end of the plunger. Plunger 5 is cannulated along its longitudinalaxis, as shown in FIG. 1. An internally threaded recess 20 is providedat the trailing end of stem portion 19 for engagement with an externallythreaded tool to remove plunger 5 from the patient's bone afterimplantation, if desired.

The body portion 17 of plunger 5 includes a raised annular lip 18adjacent the trailing end of portion 17, a groove 10 is provided in theinner wall of ring 9 and a plurality (eight in the embodiment shown inFIGS. 1 to 5) of relatively short slots 12 (open at the trailing edge ofring 9) are provided in the closed ring 9, all for a purpose to bedescribed below.

FIGS. 3 to 5 show how bone implant 1 is actuated to grip a patient'sbone B at the leading end portion of the implant. The expansion sleeve 3is inserted into and held within a cylindrical cavity C in the patient'sbone B by means of an insertion rod 21 having an externally threaded endportion 23 screwed into the internally threaded bore 15 of sleeve 3.Insertion rod 21 extends along the longitudinal axis of sleeve 3 and iscannulated to fit over a guide wire 25. Cannulated plunger 5, which isin a sliding fit over rod 21, is advanced along rod 21 towards sleeve 3(i.e. from left to right in FIG. 3) with its substantially cylindricalbody portion 17 in the leading position. After the body portion 17 ofplunger 5 first contacts the elongated strips 11 at the beginning ofregion r₂ (see FIG. 4), the continued advancement of plunger 5 into theinterior of sleeve 3 causes the eight strips 11 to expand radiallyoutwardly against the wall of the cavity C and securely grip thepatient's bone B. When the plunger 5 is fully advanced within theexpansion sleeve 3 (see FIG. 5), the raised lip 18 fits into the groove10 to lock the sleeve 3 and plunger 5 against an undesired axialdisengagement after implantation of the implant 1. The equally-spaced(circumferentially) slots 12 impart a slight resiliency to the ring 9which allows the rib 18 to snap into the groove 10. Additionally, whenthe plunger is fully advanced within the sleeve, the cylindrical wall ofthe sleeve 3 has taken on a generally barrel-shaped contour, whichresults from the fact that the opposite ends of each strip 11 are fixedto dome 7 and ring 9, respectively. Since the expansion sleeve 3 is madeof a resilient material the strips 11 expand radially outwardly inelastic deformation when the plunger 5 is fully advanced into theexpansion sleeve 3. If desired, an extrudable bone cement or bone fillermaterial can be inserted into the sleeve 3 so that when the plunger 5 isadvanced into the sleeve 3 the bone cement or bone filler is extrudedthrough the openings 13 to the sleeve-bone interface.

An insertion instrument 27 of the invention for use in the implantationof bone implant 1 is shown in FIG. 18 assembled with sleeve 3 andplunger 5. Insertion instrument 27 includes the elongatedaxially-cannulated insertion rod 21 (upon which plunger 5 can slide)having an externally threaded end portion 23 adapted to be screwed intothreaded bore 15 in dome 7 of sleeve 3 and an externally smooth portion29 extending from the threaded portion 23, a hollow sleeve 31 capable ofsliding movement upon smooth portion 29, a handle 33 and a means 35 foradvancing the hollow sleeve 31 along the smooth portion 29 of rod 21towards the externally threaded portion 23 of rod 21. The sleeveadvancing means 35 comprises a knurled knob 37 threaded upon anexternally threaded portion 39 of the elongated rod 21. As knob 37 isturned it pushes against sleeve 31. Preferably, a nylon washer (notshown in the figures) is fitted between knob 37 and sleeve 31. A guidepin 41 provided on the inner wall of sleeve 31 is received within alongitudinal groove provided in threaded portion 39 (see FIG. 18A). Inuse, the surgeon holds handle 33 in one hand and turns knob 37 with theother hand to advance hollow sleeve 31 toward the expansion sleeve 3.The hollow sleeve 31 abuts the plunger 5, which is also fitted on theinsertion rod 21, and thus in turn forces plunger 5 along the rod untilthe plunger is advanced into the expansion sleeve 3. As the cylindricalbody portion 17 of the plunger 5 is being pressed by knob 37 and hollowsleeve 31 against the elongated strips 11 of the expansion sleeve 5 andforcing the strips 11 to expand, the surgeon can stop advancement of theplunger into the expansion sleeve (to rest, to assess the surgicalsituation, or for any other reason) without relaxing the force beingplaced on the plunger by the insertion instrument 27. In such asituation movement of hollow sleeve 31 and plunger 5 along insertion rod21 away from expansion sleeve 5 is positively prevented by the structureof the sleeve advancing means 35.

After the implantation of the expansion sleeve 3 and the plunger 5 hasbeen completed, with the plunger fully advanced within the interior ofthe sleeve, the guide wire 25 and the insertion rod 21 are removed fromthe patient's bone, although it is contemplated that an appropriatelydimensioned insertion rod and/or guide wire might be left in place inthe patient's bone to form a part of the implanted elongated boneimplant.

A proximal angled side plate 43 which may be included in a modularimplant system or kit of the invention is shown in FIGS. 6 and 7.Proximal angled side plate 43 includes an elongated plate portion 45adapted to be secured to the outer cortical wall of the femoral shaftand an integral hollow sleeve 47 extending from one end of plate portion45. The elongated plate portion 45 has an upper surface 49 and a lowersurface 51 intended to be adjacent the patient's bone in use, while thehollow sleeve 47 is provided with a longitudinal cylindrical throughbore 53 extending from upper surface 49 the free end of hollow sleeve47. As shown in FIG. 7, the elongated plate portion 45 and hollow sleeve47 are oriented at an oblique angle of about 130°-150° so that hollowsleeve 47 is adapted to extend into the intertrochanteric region of thefemur when elongated plate portion 45 is secured to the outer corticalwall of the adjacent femoral shaft.

As used herein, the term "adapted to be secured to the outer corticalwall" of a bone (e.g. a femur) means that an implant is adapted to besecured to a bone in such a way that it abuts the outer cortical wall ofthe bone. As one example, an implant may be provided with a plurality ofapertures along its length for the receipt of bone fasteners (e.g. bonescrews, nails, pins, bolts, rivets, or the like) used to secure theimplant to the outer cortical wall.

As is shown in FIGS. 6 and 7, three circular through apertures 55, 57and 59 are provided in the elongated plate portion 45 of the proximalangled side plate 43 for the receipt of three bone screws, one in eachaperture. These three apertures are staggered with respect to thelongitudinal axis of plate portion 45 (see FIG. 6) in order to reducestress concentrations in the secured plate portion and in the bone. Asshown in FIG. 7, the upper portions 61 of the walls of apertures 55, 57and 59 adjacent upper surface 49 are preferably identical,concave-upward spherical surfaces. These identical spherical surfacesare adapted for cooperation with spherically-headed cortical andcancellous bone screws, as is discussed below. Two of these apertures,57 and 59, communicate with an elongated cavity 63 formed in the lowersurface 51 of plate portion 45, which cavity extends longitudinally fromthe free end 65 of plate portion to a shoulder 67. Cavity 63 is adaptedto receive an end portion of an elongated bone plate of the invention ina sliding fit, as will be described below. The lower surface 51 ofelongated plate portion 45 is slightly curved (as viewed in transversecross-sections of plate portion 45 (see FIG. 8)) to conform to the outercortical wall of a femur.

An elongated bone plate 69 of the invention adapted to be secured to apatient's bone is shown in FIGS. 9 and 10. Bone plate 69 has an uppersurface 71, a lower surface 73 intended to be adjacent the patient'sbone in use and two side surfaces 75 and 77 connecting surfaces 71 and73. Bone plate 69 is provided with for example six identical elongatedthrough apertures, e.g. 79, 80 and 85, for the receipt of bone screwsused to secure the plate to a patient's bone, e.g. to the outer corticalwall of the femoral shaft. Some other number (odd or even) of elongatedthrough apertures than six may be provided in the bone plate of theinvention, if desired. Preferably, the elongated apertures arealternately offset from the longitudinal axis of the bone plate (seeFIG. 9) in order to reduce stress concentrations in the secured boneplate and in the bone and the separation between the two centermostslots (e.g. the third and fourth slots in FIG. 9) is greater than theseparation between other pairs of adjacent slots. As can be readily seenin FIG. 10, the width of upper surface 71 is greater than the width oflower surface 73, side surfaces 75 and 77 are tapered inwardly towardone another in the direction from surface 71 to surface 73 (i.e.downwardly and inwardly in FIG. 10), and the thickness T of the boneplate 69 is substantially constant across the bone plate from sidesurface 75 to side surface 77. In the embodiment of FIGS. 9 and 10, boneplate 69 includes two parallel rails 81 and 83 located at the oppositesides of lower surface 73, which rails extend along substantially theentire length of plate 69. In use, only rails 81 and 83 contact thesurface of the patient's bone to minimize interference with bone orperiosteal vascularity.

An important feature of bone plate 69 is that its transversecross-sectional dimensions are complementary to those of the cavity 63in the elongated plate portion 45 of the proximal angled side plate 43.Thus, either end of bone plate 69 can be inserted into cavity 63, butbecause of the tapered side surfaces of the bone plate and cavity thebone plate 69 can enter and be removed from the cavity 63 only byrelative axial movement through the opening of cavity 63 at the free end65 of plate portion 45. Separation or joining by relative movement inthe vertical direction is not permitted and the bone plate 69 cannotrotate with respect to the proximal angled side plate 43 when it isinserted within the cavity 63 (see FIG. 17 for a depiction of the"dovetail" interlock between plate portion 45 and bone plate 69). Wheneither end of bone plate 69 is inserted into cavity 63 and the end ofthe bone plate abuts shoulder 67, apertures 57 and 59 in the angled sideplate 43 overlie apertures 79 and 85, respectively, in the bone plate69. Thus, with the use of two bone screws passed through the twooverlying pairs of apertures and threaded into the patient's bone, boneplate 69 can be secured to the elongated plate portion 45 of side plate43 in axial alignment in a stable and secure connection so as to providean effective extension of the length of plate portion 45 in vivo.

In a preferred modular system of the invention three bone plates ofvarying length of the type shown in FIG. 9 are provided, having four,six and eight elongated apertures respectively, for use eitherindependently or to extend the length of side plates.

Elongated bone plate 69 may also be used by itself as a conventionalbone plate in the treatment of, for example, diaphyseal femoralfractures. The six apertures in the plate are elongated to be able toreceiver either one or two screws each in use. Preferably, the upperportions 107, adjacent upper surface 71, of the identical apertures arespherically-rounded concave-upward all the way around the aperture.These identical spherically-rounded surfaces are adapted for cooperationwith spherically-headed cortical and cancellous bone screws, as isdiscussed below.

Bone plate 69 is preferably slightly curved (as viewed in transversecross-sections such as FIG. 10) to conform to the shape of the humanfemoral shaft. In the preferred embodiment shown in FIG. 10, uppersurface 71 and lower surface 73 are defined in transverse bone platecross-sections by arcs of two concentric circles having a center O,while side surfaces 75 and 77 are defined by two straight lines which,when extended, pass through center O and form together an angle A.

A pair of self-tapping cortical bone screws 89 and 91 which may beincluded in a modular implant system of the invention are shown in FIGS.11A and 11B. Screws 89 and 91 have identical heads 93 and identicalshanks 97 and 99 externally threaded along essentialy the entire shanklength, with the single exception that shank 97 of screw 89 is longerthan shank 99 of screw 91. A pair of self-tapping cancellous bone screws101 and 103 which may be included in a modular implant system of theinvention are shown in FIGS. 12A and 12B. The heads 93 of screws 101 and103 are identical to the heads of cortical screws 89 and 91, while theshanks of cancellous screws 101 and 103, which are externally threadedadjacent the free shank end only, are identical with the singleexception that the shank of screw 101 has a longer unthreaded portionthan the shank of screw 103. Another pair of self-tapping cortical bonescrews 90 and 92 are shown in FIGS. 32 and 32A. These screws areidentical to screws 89 and 91 except that a portion of the shanks ofscrews 90 and 92 is not threaded. As is shown in FIG. 13, an identicalaxially-extending recess 95 having parallel axially-extending walls isprovided in each of the identical heads 93 of screws 89, 91, 90, 92, 101and 103 for the receipt of a screw-driving instrument (e.g. ascrewdriver). The recess is generally star-shaped in cross-section, e.g.the generally star-shaped Torx ™-drive cross-section shown in FIG. 13 orthe generally star-shaped cross-section of a Pozidriv™ recess. Ifdesired, the cortical and/or cancellous bone screws may be reduced inone or more steps in diameter or tapered towards the free shank end forincreasing grip strength on the neighboring femoral cortex.

Another important feature of the design of screw head 93 is that theunderside 105 of head 93 is spherically-rounded and substantiallycomplementary with the spherically-rounded upper portions of the wallsof the screw-receiving apertures in angled side plate 43 and elongatedbone plate 69. FIG. 14 shows the permitted side-to-side angulation ofone of the four screws of FIGS. 11A, 11B, 12A and 12B (shown in phantomlines) within one of the screw-receiving apertures (i.e. aperture 80)provided in the bone plate 69. As a consequence of the substantiallycomplementary spherically-rounded surfaces of head underside 105 and theupper portion 107 of the wall of aperture 80, screw 89 is capable ofrotating through an angle of about 30° in a plane perpendicular to thelongitudinal axis of bone plate 69. Essentially unrestricted angulationis permitted in a plane parallel to the longitudinal axis of the boneplate. However, when bone screw 89 is positioned fully at the end ofaperture 80 unrestricted angulation is permitted in one direction onlyin a plane parallel to the longitudinal axis of the bone plate whileonly about a 15° rotation from the vertical is permitted in the oppositedirection in said plane. The radius of the spherically-rounded surfaceof the upper portion 61 of the apertures 55, 57 and 59 in the angledside plate 43 is equal to the radius in the transverse plane of FIG. 14of the surface of the upper portion 107 of aperture 80 of bone plate 69.Thus, screws 89, 91, 101 and 103 are capable of a universal rotationwith respect to the elongated plate portion 45 within a cone having anapex angle of about 30° when fully advanced within one of the apertures55, 57 and 59. (However, when the angled side plate is connected with anelongated bone plate this freedom of rotation is restricted considerablyfor the two screws passing through both plates.) The substantial allowedangulation of bone screws within an elongated bone plate or angled sideplate enhances capabilities for adaptation to the fixation of obliquefractures and complex fracture patterns such as butterfly fractures.This angulation permits the bone screws to extend approximately normallyto many fracture lines and serves to increase the number of bonefragments that can be directly gripped by at least one screw.

Elongated epiphyseal/metaphyseal implant 1, proximal angled side plate43, elgonated bone plate 70 having four elongated apertures and aplurality of the cortical bone screws 89 can be connected together andsecured to a patient's right femur F in the manner shown in FIGS. 15 to17 to form an angled side plate-hip assembly with the effective lengthof the elongated plate portion of the angled side plate extended by theelongated bone plate. The implant 1 is first implanted within a cavityprepared in the proximal femur, which cavity must be widened adjacentits open end to accommodate hollow sleeve 47, said sleeve 47 of sideplate 43 is then inserted into the cavity so that a portion of thecylindrical stem portion 19 of plunger 5 is received in a sliding fitwithin the cylindrical bore 53 of sleeve 47, one end of bone plate 70 isslid into cavity 63 of side plate 43 until it abuts shoulder 67, and theentire assembly is then secured to the femur F with a plurality ofcortical bone screws 89 passed through apertures in side plate 43 andbone plate 70. If desired, one or more conventional fixation pins (e.g.Knowles pins) unconnected to implant 1 and angled side plate 43 may alsobe implanted, with an orientation substantially parallel to theorientation of implant 1 shown in FIG. 16. Bone plate 70 can, of course,be omitted from the assembly of FIG. 16 if the length of plate portion45 is sufficient without extension in a particular surgical situation.

A femoral intramedullary rod 109 which may be included in a modularimplant system or kit of the invention is shown in side elevationalviews of FIGS. 19 and 20 as viewed in perpendicular directions. Rod 109has a proximal end 111 and a distal end 113 and a pair of transversethrough bores 115 adjacent distal end 113 to receive bone screws 90. Oneor two through bores 116 to receive locking bone screws may also beincluded adjacent proximal end 111. Rod 109 has a distal end portion 117and a straight proximal end portion 119. As is shown in FIG. 19, rod 109has a slight bow, which is intended to lie in the anterior-posteriorplane of the femur after implantation; no such bow is exhibited in FIG.20, since rod 109 is intended to be straight in the lateral-medial planeafter implantation. The transverse cross-section of rod 109 is shown inFIG. 21. This cross-section has a closed profile, with the outerperiphery of the cross-section being a plurality of (e.g. six) smoothlyrounded peaks (e.g. 121), all terminating on the same first circle,connected by an equal number of smoothly rounded valleys (e.g. 123), allbottoming on the same second circle concentric with and of smallerdiameter than said first circle. The provision of these alternatingpeaks and valleys greatly enhances the stability of the implanted rod109 against axial rotation with respect to the patient's bone, whiletheir smoothly rounded nature greatly reduces the possibilities fordamaging the bone of the intramedullary wall. Furthermore, thealternately raised and lowered outer peripheral rod configuration shownin FIG. 21 provides for extensive re-vascularization of the bone tissueof the intramedullary canal wall following reaming. FIG. 21 also showsthat rod 109 is axially cannulated, with an axial bore 125 extendingfrom the distal tip 127 of hollow rod 109 to the proximal tip 129 of therod. A diametrical slot 120 is provided at proximal tip 129 forengagement with appropriate insertion and extraction tools.

An elongated connection piece 139, locking screw 141 and locking shoe142 for connecting an epiphyseal/metaphyseal implant 1 to intramedullaryrod 109 adjacent to the proximal end 111 of rod 109 to form a Y-nailtype of assembly are shown in FIGS. 23 and 24. Connection piece 139 isprovided at one end with an elongated cylindrical cavity 143 alignedwith the longitudinal axis of piece 139 and adapted to receive the freeend of stem portion 19 of plunger 5 of implant 1 in a sliding fit.Connection piece 139 is also provided with a cylindrical through bore145 disposed at an oblique angle of about 135° with respect to saidlongitudinal axis, and an elongated partially countersunk and partiallyinternally-threaded bore 147 aligned with said longitudinal axis at theend of the elongated connection piece 139 opposite to cavity 143. Bore147 is adapted to receive locking screw 141 and locking shoe 142, andboth bore 147 and cavity 143 open into through bore 145. The diameter ofthrough bore 145 is just slightly greater than that of the maximumcross-sectional dimension of the proximal end portion 119 ofintramedullary rod 109 so that proximal end portion 119 can be receivedin a close sliding fit within through bore 145 permitting rotational andtranslational adjustment of the connection piece 139 with respect to theintramedullary rod 109. Connection piece 139 and intramedullary rod 109can be securely locked against relative translational and rotationalmovement by screwing locking screw 141 forward in the partially threadedbore 147 behind the locking shoe 142 until the leading surface 144 oflocking shoe 142 very firmly presses against the surface of proximal endportion 119, and then unlocked again if desired simply by unscrewing141. The leading surface 144 of locking shoe 142 has a grooved contouradapted to fit closely and mesh with the splined external contour of rod109, thereby enhancing the secure locking of rod 109 to the connectionpiece 139. Locking screw 141 and locking shoe 142 are assembled togetherin use, e.g. by a captured thread or staked head connection, to causewithdrawal of shoe 142 when screw 141 is unscrewed while permittingindependent relative rotation between these two element during screwingand unscrewing of screw 141.

In the alternative embodiment shown in FIG. 22, a hollow sleeve 131having a smooth cylindrical outer surface is detachably secured to theexterior of the proximal end portion 119 of intramedullary rod 109(having the fluted cross-section of FIG. 21) by means of a locking screw135 having a head and an externally threaded shank fitted through acentrally-disposed opening in the top wall of sleeve 131 and threadedinto an internally-threaded centrally-disposed bore 137 at the top ofrod 109. An advantage of the embodiment of FIG. 22 is that the diameterof the straight proximal end of rod 109 is effectively increased abovethat of the maximum transverse dimension in the transverse cross-sectionof FIG. 21. The hollow sleeve 131 should extend distally at least to thepoint of maximum applied bending moment in normal use, which point ofmaximum bending moment is usually in the subtrochanteric region of thefemur, but not all the way to the midway point along the length of rod109 between the distal and proximal tips 127 and 129 of the rod. Whenhollow sleeve 131 is used, the contour of the leading surface of lockingshoe 142 should be adapted accordingly, or alternatively, the lockingshoe can be eliminated and the locking screw used alone.

Intramedullary rod 109, connection piece 139, locking screw 141, lockingshoe 142 and a bone implant 1 can be connected together in the mannershown in FIG. 25 to form a Y-nail type of assembly in a femur F, withimplant 1 and piece 139 forming together the elongated cross-member ofthe Y-nail. The epiphyseal/metaphyseal implant 1 is first implanted intoa cavity prepared in the proximal femur, which cavity must be widenedadjacent its open end to accommodate the connection piece 139. Piece 139is then advanced into the prepared bone cavity and oriented so that aportion of stem portion 19 of plunger 5 is received in a sliding fitwithin cavity 143 and through bore 145 is in approximate alignment withthe femoral intramedullary canal. Rod 109 is advanced distally throughan opening prepared by conventional means in the proximal femur wall andthrough the through bore 145 in piece 139 until the distal end portion117 of rod 109 is in the distal femur and the proximal end portion 119of the rod 109 is within the through bore 145. The disposition of rod109 with respect to the femur F and connection piece 139 is thencarefully adjusted to the desired diposition, and connection piece 139is then locked to intramedullary rod 109 by means of the locking screw141 and locking shoe 142. If desired a cortical bone screw 90 of thetype shown in FIG. 32A of large shank length can be inserted byconventional methods through one or both of the transverse bores 115 tolock the rod 109 to the distal femur. Also, cap screw 135 may be screwedinto bore 137, even when sleeve 131 is not being used, to prevent boneingrowth into the threads in bore 137.

It is contemplated that a connection piece similar to piece 139 could beused, if desired, to connect an epiphyseal/metaphyseal implant similarto implant 1 to the distal end portion 117 of intramedullary rod 109,with the epiphyseal/metaphyseal implant residing in the distal condylarregion of the femur and being substantially perpendicular to saidportion 117. In such a case the through bore of the connection pieceanalogous to through bore 145 in piece 139 would be substantiallyperpendicular to the longitudinal axis of the connection piece.

A distal angled side plate 149 which may be included in a modularimplant system or kit of the invention is shown in FIGS. 26 and 27.Distal angled side plate 149 includes an elongated plate portion 151adapted to be secured to the outer cortical wall of the distal femoralshaft and an integral hollow sleeve 153 extending from one end of plateportion 151. As is shown in FIG. 27, the plate portion 151 is slightlyangulated in the vicinity of line R in order to accommodate thecommencement of the anatomical bulge of the lateral distal femur. Theelongated plate portion 151 has an upper surface 155 and a lower surface157 intended to be adjacent the patient's bone in use, while the hollowsleeve 153 is provided with a longitudinal cylindrical through bore 159extending from upper surface 155 to the free end of hollow sleeve 153.As shown in FIG. 27, the elongated plate portion 151 and hollow sleeve153 are substantially perpendicular so that hollow sleeve 153 is adaptedto extend into the distal condylar region of the femur when elongatedplate portion 151 is secured to the outer cortical wall of the adjacentdistal femoral shaft. Through bore 159 is dimensioned to receive aportion of the stem portion 19 of the plunger 5 of an elongatedepiphyseal/metaphyseal implant 1 in a sliding fit. The lower surface 157is slightly curved in transverse cross-section in a similar manner asshown in FIG. 8 (for the proximal side plate 43) to conform to the outercortical wall of a distal femur.

Three circular through apertures 161, 163 and 165 are provided in plateportion 151 for the receipt of three bone screws (e.g. cortical screw89), one in each aperture. These three apertures are staggered withrespect to the longitudinal axis of plate portion 151 (see FIG. 26) inorder to reduce stress concentrations in the secured plate portion andin the bone. Apertures 161, 163 and 165 are identical respectively toapertures 55, 57 and 59 in the proximal angled side plate 43. The distalangled side plate 149 is also provided with an elongated cavity 167formed in the lower surface 157 of plate portion 151. Cavity 167 isidentical to cavity 63 in the proximal angled side plate 43. Thus,cavity 167 is adapted to receive either end of elongated bone plate 69in a "dovetail" interlocked sliding fit (see FIG. 17), and when the endof the bone plate abuts shoulder 169 apertures 163 and 165 overlie thetwo terminal apertures, e.g. apertures 79 and 85 respectively, in thebone plate 69.

The distal angled side plate 149, an elongated epiphyseal/metaphysealimplant 1 and a plurality of the cortical bone screws 89 can beconnected together and secured to the patient's femur F in the mannershown in FIG. 28 to form a distal side plate-pin assembly with theeffective length of the elongated plate portion of the side plateextended by the elongated bone plate. The preferred surgical procedureis analogous to the one described above with regard to the assembly ofFIGS. 15 and 16. Bone plate 69 can, of course, be omitted from theassembly of FIG. 28 if the length of plate portion 151 is sufficientwithout extension in a particular surgical situation.

A distal buttress plate 171 of the invention adapted to be secured tothe outer cortical wall of the lateral distal femur is shown in FIGS. 29and 30. Buttress plate 171 includes a relatively flat elongated proximalportion 173 adapted to be secured to the lateral distal femoral shaftand a three dimensionally-contoured distal portion 175 designed toreplicate the mean geometry of the lateral femoral condyle of adulthumans. The distal portion 175 includes a generally rounded head 177 atthe distal end of plate 171, a generally widened body 179 having agreater maximum width than both head 177 and proximal portion 173, and aneck 181 having a minimum width W substantially smaller than the maximumwidths of head 177 and body 179. As viewed in transverse cross-sections,the lower surface of the distal buttress plate 171 is contoured alongits entire length to conform to the outer cortical wall of the distalfemur.

Distal buttress plate 171 is adapted to be secured to the outer corticalwall of the lateral distal femur by means of bone screws received inapertures in the plate. Thus, three circular through apertures 183, 185and 187 are provided in proximal portion 173 for the receipt of threebone screws (e.g. cortical screw 89), one in each aperture. These threeapertures are staggered with respect to the longitudinal axis ofproximal portion 173 (see FIG. 29), and are identical respectively toapertures 55, 57 and 59 in the angled side plate 43. Also, an elongatedaperture 189 is provided in head 177 and two elongated apertures 191 and193 are provided in body 179, one on each side of body 179. Each ofapertures 189, 191 and 193 is substantially identical to the aperturesin the elongated bone plate 69 and thus are each configured to receivetwo (or one, if only one is desired) bone screws having a head 93 andpermit the universal angulation of said screws when fully advanced inthe aperture.

Furthermore, it is often highly desirable to use a distal buttress platein conjunction with a pair of fracture reduction lag screws extendingacross the distal condylar region of the femur. Such lag screws arescrewed fully into the bone before the distal buttress plate isimplanted and thus cannot practically be passed through the plate. Animportant feature of distal buttress plate 171 is that the distalportion 175 thereof is configured in such a manner that spaces outsidethe periphery of plate 171 are left against neck 181 for theaccommodation of two fracture reduction lag screws, extending across thedistal condylar region of the femur, on the two sides of neck 181. Thesetwo lag screws are shown in phantom in FIG. 29 as elements 195 and 197.

Finally, the distal buttress plate 171 is also provided with anelongated cavity 199 formed in the lower surface of the proximal portion173. Cavity 199 is identical to, and is adapted to serve in the samebone plate-"dovetail" interlocking capacity as, cavity 63 in the angledside plate 43 and cavity 167 in the angled side plate 149. When the endof bone plate 69 inserted into cavity 199 abuts the shoulder 201 of thecavity, apertures 185 and 187 overlie the two terminal apertures, e.g.apertures 79 and 85 respectively, in the bone plate 69.

Distal buttress plate 171, elongated bone plate 69, a plurality ofcortical bone screws such as screw 89 and a plurality of cancellous bonescrews such as screw 101 can be connected together and secured to apatient's femur F in the manner shown in FIG. 31. First, two lag screws(not shown in FIG. 31) are fully implanted in the distal condylarregion, if desired, to reduce a fracture in said region. These implantedlag screws are positioned so that they lie generally in thelateral-medial plane and are spaced so that they will lie in closeproximity to the two opposite sides of the neck 181 of portion 175 (seeFIG. 29). The distal buttress plate 171 is then secured to the lateralfemur, with neck 181 fitting between the two previously implantedfracture reduction lag screws, by means of bone screws 101 passingthrough apertures 189, 191 and 193 (one or two screws can be passedthrough each of apertures 189, 191 and 193, as desired) and a bone screw89 passed through aperture 183. Bone plate 69 is then slid into cavity199 until its end abuts shoulder 201 and bone screws 89 are screwed tothe femur F through apertures 185 and 187. Finally, bone screws 89 arescrewed to the femur F through some or all of the four apertures of boneplate 69 remaining outside of the cavity 199. Distal buttress plate 171can, of course, be implanted without bone plate 69 if the length of theproximal portion 173 is sufficient without extension for a particularsurgical situation.

We claim:
 1. An assembly for the stabilization of a fractured femurcomprising:an elongated cross-member having a leading portion adapted tobe received within a cavity in and grip the femoral head and a trailingportion adapted to extend from the leading portion through the femoralneck into the intertrochanteric region of a patient's femur, with saidtrailing portion being provided with a cylindrical through bore, saidthrough bore being at an oblique angle with respect to the longitudinalaxis of the cross-member so that it can be brought into approximatealignment with the femoral intramedullary canal when the leading portionof the cross-member is inserted into the femoral head; an intramedullaryrod having a distal end portion and a proximal end portion, with themaximum cross-sectional dimension of said proximal end portion beingjust slightly less than that of said cylindrical through bore in thetrailing portion o the cross-member so that said proximal end portion ofthe intramedullary rod can be received in a close sliding fit withinsaid through bore permitting rotational and translational adjustment ofthe cross-member with respect to the intramedullary rod, said elongatedcross-member comprising an elongated bone implant having a leadingportion adapted to grip the femoral head and a trailing portion, and anelongated connection piece non-integral with said bone implant, withsaid trailing portion of said elongated bone implant adapted to bereceived within a bore in said connection piece, and with saidintramedullary rod-receiving cylindrical cross-member through bore beingin said connection piece; and distinct, positive and active means toreleasably lock the elongated connection piece and intramedullary rod toprevent their relative translational and rotational movement whenassembled together.
 2. An assembly of claim 1 comprising a plurality ofsaid elongated cross-members of varying lengths.
 3. An assembly of claim1 wherein said proximal end portion of the intramedullary rod issubstantially straight and said intramedullary rod comprises asubstantially straight and substantially cylindrical hollow sleeveadapted to be detachably secured at the proximal end portion of theintramedullary rod and having a substantially smooth outer surface, withsaid sleeve, when so secured, extending at least to the point of maximumapplied bending moment in normal use but not up to the midway pointalong the rod between its distal and proximal tips, said point ofmaximum bending moment applied to the intramedullary rod being in thesubtrochanteric region of the femur.
 4. An assembly of claim 1 whereinsaid elongated cross-member and said intramedullary rod are made of aresilient titanium-base alloy.
 5. An assembly of claim 1 wherein saidintramedullary rod is hollow and has a closed profile in transversecross-section along substantially its entire length, and the outerperiphery of the transverse cross-section of said intramedullary rod isa plurality of smoothly rounded peaks, all terminating on the same firstcircle, connected by a plurality of smoothly rounded valleys, allbottoming on the same second circle concentric with and of smallerdiameter than said first circle.
 6. An assembly of claim 1 wherein saidintramedullary rod has a longitudinally-splined external contour andsaid releasable locking means comprises a locking screw and a lockingshoe adapted to fit within an at least partially threaded bore in saidelongated connection piece with said locking shoe between said lockingscrew and said cylindrical through bore, with said locking shoepresenting a surface opposite said locking screw having a groovedcontour adapted to fit closely and mesh with the splined externalcontour of said intramedullary rod, whereby said locking screw can beadvanced by screwing said screw within said at least partially threadedbore so as to firmly press said grooved-contoured surface of saidlocking shoe against the longitudinally-splined exterior contour of saidintramedullary rod.
 7. An assembly for the stabilization of a fracturedfemur comprising:an elongated cross-member having a leading portionadapted to be received within a cavity in and grip the femoral head anda trailing portion adapted to extend from the leading portion throughthe femoral neck into the intertrochanteric region of a patient's femur,with said trailing portion being provided with a cylindrical throughbore, said through bore being at an oblique angle with respect to thelongitudinal axis of the cross-member so that it can be brought intoapproximate alignment with the femoral intramedullary canal when theleading portion of the cross-member is inserted into the femoral head;an intramedullary rod having a distal end portion and a proximal endportion, with the maximum cross-sectional dimension of said proximal endportion being just slightly less than that of said cylindrical throughbore in the trailing portion of the cross-member so that said proximalend portion of the intramedullary rod can be received in a close slidingfit within said through bore permitting rotational and translationaladjustment of the cross-member with respect to the intramedullary rod;and distinct, positive and active means to releasably lock the elongatedcross-member and intramedullary rod to prevent their relativetranslational and rotational movement when assembled together, whereinsaid intramedullary rod has a longitudinally-splined external contourand said releasable locking means comprises a locking screw and alocking shoe adapted to fit within an at least partially threaded borein said elongated cross-member with said locking shoe between saidlocking screw and said cylindrical through bore, with said locking shoepresenting a surface opposite said locking screw having a groovedcontour adapted to fit closely and mesh with the splined externalcontour of said intramedullary rod, whereby said locking screw can beadvanced by screwing said screw within said at least partially threadedbore so as to firmly press said grooved-contoured surface of saidlocking shoe against the longitudinally-splined exterior contour of saidintramedullary rod.
 8. An assembly of claim 1 wherein said elongatedbone implant comprisesan integral substantially cylindrical expansionsleeve having a smoothly rounded circumferentially-closed dome at oneend, a circumferentially-closed circular ring at its other end, and aplurality of thin elongated strips extending between, and connected attheir opposed ends by, said circumferentially-closed dome and ring, withsaid plurality of strips defining together a cylindrical sleeve wall,said strips being of varying radial thickness along their length andhaving textured outer surfaces, and said cylindrical sleeve wall havingin the rest position of the sleeve an outer diameter equal to the outerdiameter of the circular ring, an inner diameter adjacent said ringequal to the inner diameter of said ring and an inner diameter in aregion spaced from said ring reduced from the inner diameter of saidring; and an elongated plunger having at one end thereof a substantiallycylindrical body portion having a diameter essentially equal to theinner diameter of said circumferentially-closed circular ring of theexpansion sleeve, said elongated plunger also having a cylindrical stemportion extending from said substantially cylindrical body portion tothe other end of the plunger, with the diameter of said cylindrical stemportion being less than the diameter of said substantially cylindricalbody portion, whereby when said expansion sleeve is held in a cavity ina bone fragment on one side of a fracture and the plunger is theadvanced through said circular ring and into the interior of said sleevewith its substantially cylindrical body portion in the leading position,said plurality of strips having textured outer surfaces are caused toexpand radially outwardly and thereby securely grip said bone fragment,with said stem of said elongated plunger being adapted to be received ina sliding fit within a cylindrical bore in said connection piece.
 9. Abone implant for use in the stabilization of a bone fracturecomprisingan integral substantially cylindrical expansion sleeve havinga smoothly rounded circumferentially-closed dome at one end, acircumferentially-closed substantially inextensible circular ring at itsother end, and a plurality of thin elongated strips extending between,and connected at their opposed ends by, said circumferentially-closeddome and ring, with said plurality of strips defining together acylindrical sleeve wall, said strips being of varying radial thicknessalong their length and having textured outer surfaces, and saidcylindrical sleeve wall having in the rest position of the sleeve anouter diameter equal to the outer diameter of the circular ring, aninner diameter adjacent said ring equal to the inner diameter of saidring and an inner diameter in a region spaced from said ring reducedfrom the inner diameter of said ring; and an elongated plunger having atone end thereof a substantially cylindrical body portion having adiameter essentially equal to the inner diameter of saidcircumferentially-closed circular ring of the expansion sleeve, wherebywhen said expansion sleeve is held in a cavity in a bone fragment on oneside of a fracture and the plunger is then advanced through saidcircular ring and into the interior of said sleeve with itssubstantially cylindrical body portion in the leading position, saidplurality of strips having textured outer surfaces are caused to expandradially outwardly and thereby securely grip said bone fragment.
 10. Abone implant of claim 9 wherein said dome is provided with means forsecuring an elongated rod thereto so that said rod extends within saidexpansion sleeve and through said ring along the longitudinal axis ofsaid sleeve and can thereby be used to insert and hold said expansionsleeve in said cavity, and said plunger is cannulated along itslongitudinal axis to receive said elongated insertion rod.
 11. A boneimplant of claim 10 wherein said insertion rod securing means isreleasable.
 12. A bone implant of claim 11 wherein said means forreleasably securing an elongated insertion rod to said dome comprises acentrally-disposed threaded axial through bore provided in said dome.13. A bone implant of claim 9 wherein said plurality of strips areresilient and expand radially outwardly in elastic deformation when saidplunger is advanced into the interior of said sleeve.
 14. A bone implantof claim 13 wherein said expansion sleeve is made of a resilienttitanium-base alloy.
 15. A bone implant of claim 14 wherein saidtitanium base alloy consists essentially of about 11.5 percent by weightmolybdenum, about 6 percent by weight zirconium, about 4.5 percent byweight tin and the balance titanium.
 16. A bone implant of claim 14wherein said titanium base alloy consists essentially of about 6 percentby weight aluminum, about 4 percent by weight vanadium and the balancetitanium.
 17. A bone impact of claim 9 wherein said elongated plungerhas a cylindrical stem portion extending from said substantiallycylindrical body portion to the other end of the plunger, with thediameter of said cylindrical stem portion being less than the diameterof said substantially cylindrical body portion.
 18. A bone impact ofclaim 9 in combination with means for connecting said plunger to anotherbone fragment on the other side of the fracture.
 19. A bone implant ofclaim 18 wherein said plunger connecting means comprises a hollow sleevedimensioned to receive said plunger in a sliding fit, said hollow sleevebeing an integral portion of an angled side plate secured to said otherbone fragment.
 20. A bone implant of claim 9 wherein the expansionsleeve is adapted to fit within a cavity formed within a femoral headand the plunger is adapted to extend, when inserted into the expansionsleeve, through the femoral neck into the intertrochanteric region ofthe femur.
 21. A bone impact of claim 9 wherein the expansion sleeve isadapted to fit within a cavity formed within the medial condylar regionof a distal femur and the plunger is adapted to extend, when insertedinto the expansion sleeve, into the lateral condylar region of saiddistal femur.
 22. A bone implant of claim 9 wherein a plurality ofopenings are provided in said expansion sleeve, in the rest position ofsaid sleeve, so that an extrudable material placed within said expansionsleeve can be extruded through said openings when the plunger isadvanced into the interior of the expansion sleeve.
 23. A bone implantof claim 9 comprising additionally cooperating means on said plungerbody portion and said expansion sleeve to lock said expansion sleeve andelongated plunger against axial disengagement after implantation of saidimplant.
 24. A bone implant of claim 23 wherein said locking meanscomprises a raised annular lip on said plunger body portion and a grooveprovided in the inner wall of said sleeve circular ring, with said lipadapted to fit into said groove in a snap fit when said plunger is fullyadvanced within said sleeve.